1. Field of the Invention
The present invention relates to a slurry electrode for use in flow energy storage systems, and a high-capacity slurry electrode-based flow energy storage system. More particularly, the present invention relates to a slurry electrode greatly improved in capacity, and a flow energy storage system based on the same.
2. Description of the Related Art
Recently, the demand and supply of energy is apt to be unstable because the prices of fossil fuels, such as petroleum, coal, etc., which are the main raw materials for electric power production, erratically change, and also because the rate of exchange frequently changes. In addition, high oil prices, and entry into the age of forced reduction of greenhouse gas emissions have increased the price of electric power production. For these reasons, there is a need for a national energy management system. The greenhouse gas that is emitted with the use of conventional energy sources, such as fossil fuels, is found to serve as a main factor of ecocide and environmental pollution. New renewable energy, such as wind force, solar energy, tidal force, etc, have attracted intensive attention as an alternative for solving the problems with conventional energy sources. Highly sensitive to weather conditions, however, electric power production from new renewable energy is impossible to maintain at constant and uniform levels. Due to this disadvantage, new renewable energy cannot be directly applied to existing electrical grid systems. For overcoming the problem, a medium-to-large capacity energy storage system is required. Medium-to-large capacity secondary cells find applications in various fields including the storage of new renewable energy, green cars, green homes, etc.
For medium-to-large capacity secondary cells, price and stability are very important factors. Lithium ion cells are very difficult to develop into MWh-level energy storage systems for power plants and distributed generation because of process difficulty in stably achieving a large area/high capacitance, cost, etc. Particularly, one of the main difficulties in implementing a smart grid for spreading new renewable energy is to alternate energy sources in real time in response to a rapid change in electric power production from new renewable energy, without reducing quality of electric power. Exhibiting limited charge/discharge rates in addition to being low in capacity for holding a charge after a single charging session, currently used secondary cells have high difficulty in receiving peak power.
Recently, Professor Gogotsi and his research team at Drexel University, USA have reported a new energy storage system, called electrochemical flow capacitor (EFC). As an electric double-layer capacitor (EDLC), the electrochemical flow capacitor is expected to achieve a higher energy density, compared to conventional solid electrode-type super capacitors, because it is found to increase the capacitance of storage tanks employing flow electrodes in a slurry state (slurry electrodes) while retaining the advantages of super capacitors including high output, longevity and stability. However, the capacitance limit of the slurry electrode is a barrier to increasing energy densities to that of lithium secondary cells.